The present invention relates to an improved medicament inhalator. More particularly, the present invention relates to a dry powder medicament inhalator usable by asthmatics and the like in such a manner to facilitate proper deposition of the medicament in the lungs. By inhaling on a mouthpiece, a prescribed dosage of medicament becomes available to the patient during the proper phase of inspiration to maximize deposition of the medicament in the lungs of the user.
The widespread existence of asthma and other respiratory disorders which inhibit proper breathing has lead to the development of numerous medications which can be used to open restricted breathing passages and to enable the user to breathe more freely. Some asthmatics suffer from only occasional attacks. Other asthmatics suffer from attacks which are relatively minor and do not cause a serious inconvenience. For others, however, breathing is a constant struggle which would be nearly impossible without the appropriate medication. These medications may be in either dry or liquid form, depending on the type of medication.
There are essentially two types of inhalation devices currently available in the marketplace for the administration of a medicament to the lungs. The predominant inhalation device is a pressurized, metered dose inhaler containing a suspension of drug in a pharmaceutically inert liquid propellant, e.g., chlorofluorocarbons or fluorocarbons. Inhalation devices of this type are well known in the art and are commonly used.
These propellant-based inhalation devices have the advantage of consistently delivering a predetermined dose of medication form the aerosol canister. However, the drug particles are propelled at high velocity from the inhalation device. A significant quantity of the medication impacts tissue in the mouth or throat of the patient, becoming unavailable for deposition in the lungs. Further, growing concern over the link between depletion of atmospheric ozone and chlorofluorocarbon propellants has focused attention on the development of alternative means of delivering medication to the lungs, including the development of dry powder inhalation systems.
Dry powder inhalers represent the second major type of inhalation devices. Dry powder inhaler devices known to the applicants and existing in the marketplace utilize the patient""s inhaled breath as a vehicle to transport the dry powder drug to the lungs. Presently there are four principal methods in use to provide fine particulate powder to the lungs without the use of chlorofluorocarbons or other propellants.
The first method available relies on the use of a hard gelatin capsule which contains a premeasured dose of therapeutically active material and an inhalator device for use with the capsule. The capsule is placed in the inhalator device which serves to open or perforate the capsule, exposing the dose of medicament. The medicament is removed from the capsule by the vacuum action created when the patient inhales through the mouthpiece of the device, and is entrained in the inspired air stream for transport to the patient""s lungs. The empty capsule is removed from the inhalation device after each use.
Inhalators using this type of capsule technology are described in U.S. Pat. No. 3,807,400 (Cocozza); U.S. Pat. No. 3,906,950 (Cocozza); U.S. Pat. No. 3,991,761 (Cocozza) and U.S. Pat. No. 4,013,075 (Cocozza). The intent in each of these devices is to remove all of the powdered medicament from the interior of the capsule. However, it has been found that the air stream generated by the patient is typically insufficient to accomplish complete removal of medicament from the capsule. This may be especially true for a patient having reduced inhalation ability due to an asthma attack. Further, gelatin capsules are affected by relative humidity during storage and may become hydrated in moist environments. Hydration results in poor opening of the capsule and agglomeration of the powder contents, or dehydrated, resulting in brittle fracture of the capsule, potentially making fine gelatin fragments available for inhalation or compromising dosing due to electrostatic attraction of medicament to the capsule surfaces.
A second method for delivery of dry powder medicaments relies on providing a package containing multiple doses of medicament, each contained in a sealed blister. The package is used in conjunction with a specially designed inhalation device which provides a means of attachment for the package and perforation of an individual blister by the patient prior to the inhalation of its contents. Delivery systems of this type are described in EPO Patent Application Publication No. 0 211 595 A2 (Newell et al.); EPO Patent Application Publication No. 0 455 463 A1 (Velasquez et al.); and EPO Patent Application Publication No. 0 467 172 A1 (Cocozza et al.). As the patient inhales, a portion of the inhaled air stream flows continuously through the perforated blister entraining the medicament and providing for inclusion of the medicament in the inspired breath. Delivery of medicament to the patient""s inspired air stream begins as sufficient flow develops through the blister for removal of the medicament. No means is provided by which the point or rate of delivery of medicament to the patient is controlled.
A third method for delivery of dry powder medicaments involves the use of a device equipped with a drug reservoir containing sufficient medicament for a much larger number of doses. The Draco TURBUHALER(copyright) is an example of this type of device and is described in detail in U.S. Pat. No. 4,688,218 (Virtanen); U.S. Pat. No. 4,667,668 (Wetterlin); and U.S. Pat. No. 4,805,811 (Wetterlin). The device provides a means for withdrawing a dose of medicament from the reservoir and presenting the withdrawn dose for inhalation by the patient. As the patient inhales through the mouthpiece of the device, the medicament contained in perforations in a dosing plate is entrained in the inspired air and flows through a conduit or conduits. The conduits serve as a vortex creating a means for breaking up powder agglomerates before the medicament becomes available to the patient. Moisture ingress in the reservoir results in agglomeration of the powder contents, compromising dosing due to retention of powder in the perforations in the dosing plate and potentially inadequate breakup of particulates in the inspired air stream.
A fourth method for delivery of dry powder medicaments involves the use of a piston to provide air for either entraining powdered medicament, lifting medicament from a carrier screen by passing air through the screen, or mixing air with powder medicament in a mixing chamber with subsequent introduction of the powder to the patient through the mouthpiece of the device. Devices of this general type are described in PCT WO 93/12831 (Zirerenberg et al.); German Patent No. DE 4133274 A1 (Kxc3xchnel et al.); German Patent No. DE 4020571 A1 (Hochrainer et al.); and U.S. Pat. No. 5,388,572 (Mulhauser et al.). The incorporation of a piston system, in each case, adds to the complexity of the inhalation device, both in terms of use by the patient and device manufacturability.
Thus, there is a need for an improved medicament inhalator wherein the availability of the medicament is controlled to ensure that the medicament is properly deposited in the lungs. Such a device preferably should be configured to release medicament into the inspired air stream during inhalation when a defined inhalation rate has been achieved. Such a device should also ensure that medicament agglomerations and medicament carried agglomerations are broken up before reaching the patient to ensure delivery of a consistent dose of medicament to the patient. In addition, the device should enable repeated use without redosing, or redosing in a manner which is convenient and unlikely to interfere with the use of the device when the user is undergoing an asthma attack.
It is an object of the present invention to provide a medicament inhalator for the administration of dry powder medicament which controls when the medicament is made available for inhalation, thereby maximizing delivery of the medicament to the lungs. The medicament may be pure drug particles, or may be drug particles attached to a carrier particle, e.g. lactose.
It is another object of the present invention to provide such a medicament inhalator which is easy to use and which has either multiple dosing capabilities, or the ability to be conveniently reloaded.
It is still another object of the present invention to provide such a medicament inhalator which is mechanically simple, does not require depletable power sources and which is relatively inexpensive.
It is yet another object of the present invention to provide such a medicament inhalator which prevents the inhalation of large agglomerations or aggregations of medicament, thereby achieving improved consistency in dosing.
The above and other objects of the invention are realized in specific illustrated embodiments of a medicament inhalator having a body with a primary inhalation passage and a secondary inhalation passage disposed therethrough. The primary inhalation passage is formed by a first inhalation channel having a proximal end and a distal end, and a restricting flap or vane disposed between the distal and proximal ends. The restricting vane is rotatably disposed within the primary inhalation passage to selectively inhibit the flow of air through the first inhalation channel. Thus, as the user inhales, drawing air from the proximal end to the distal end of the first inhalation channel, the rotatable vane rotates into a position to occlude a substantial portion of the channel, thereby limiting flow through the channel.
The secondary inhalation passage is configured to receive a medicament dosing in communication therewith. The secondary inhalation passage includes a second inhalation channel, and the medicament dosing device holds a dose of medicament in fluid communication with the second inhalation channel such that air traveling through the second inhalation channel entrains the medicament for delivery to the patient.
In accordance with one aspect of the invention, the second inhalation channel preferably has a blocking member which is biased or otherwise normally disposed in a closed position. In the closed position, the blocking member prevents airflow through the second inhalation channel. The blocking member is selectively movable into an open position wherein the block member allows airflow through the second inhalation channel.
In accordance with another aspect of the invention, the blocking member is connected to the rotatable vane disposed in the first inhalation channel. When the user of the inhalator inhales, the rotatable vane rotates into a position wherein it substantially reduces or inhibits airflow through the first inhalation channel. This same action causes the blocking member to be moved into the open position and allows airflow through the second inhalation channel. As air rushes through the second inhalation channel, the medicament disposed in fluid communication with the second inhalation channel is entrained in the air and carried to the user. Thus, the medicament is provided to the user when the rate of inhalation is sufficient to ensure delivery of the medicament to the user""s lungs. Thus, little medicament is wasted by being deposited along the mouth and throat of the person using the device.
In accordance with another aspect of the invention, the inhalation device provides for the administration of dry powder medicaments by temporarily diverting inspiratory flow from the first (primary) inhalation channel to the second (secondary) inhalation channel. By providing the inhalation device with a second inhalation channel which is sufficiently smaller than the primary inhalation channel and which is nonlinear, airflow through the secondary inhalation channel is relatively vigorous and turbulent when the blocking member is moved out of the blocking position. The vigorous airflow helps to entrain the medicament, while promoting deagglomeration of the medicament particles, deagglomeration of the medicament/carrier particles and facilitating drug particle removal from the carrier particles. Additionally, the nonlinear second inhalation channel may be formed with a portion specifically configured to form an impact surface (s). As the particles of medicament are forcefully drawn through the second inhalation channel, they collide with the impact surface, thereby breaking up any agglomeration of the medicament particles, any agglomeration of the medicament/carrier particles, and facilitating drug particle removal from the carrier particles.
In the alternative to the above, a deaggregation channel may be disposed along the primary inhalation passage to break up aggregations of medicament which are entrained by the airflow. The deaggregation channel may utilize sharp turns in direction or a zig-zag like flow pattern to cause aggregations to be impacted against side walls and thereby ensure that particle size is kept reasonably small.
In accordance with another aspect of the present invention, the medicament inhalator may be configured for use with a medicament disk having a plurality of blisters containing the medicament thereon. At or before the beginning of inhalation, the user presses a lancing mechanism to puncture a blister containing medicament. Preferably, the medicament disk is positioned along the secondary inhalation passage such that at least some of the air drawn through the secondary inhalation passage passes through the blister, and thereby ensures that nearly all of the medicament is carried to the user.
In accordance with yet another aspect of the present invention, the medicament inhalator may be configured to receive a windable tape. The windable tape is provided with a plurality of dosing units, typically in the form of small blisters filled with medicament along the tape. With each use of the medicament inhalator, the tape is drawn through the inhalator. Once all of the dosing units on the tape have been consumed, the tape is replaced.
In accordance with still another aspect of the present invention, the medicament is provided by a replaceable dosing cartridge which contains bulk powdered medicament in a reservoir. Before or during each use, the dosing cartridge is accessed in such a manner as to provide a desired dose of medicament. The dose is disposed in fluid communication with the secondary inhalation passage so that the medicament will be entrained in air flowing therethrough and be carried to the lungs of the user.
In accordance with still yet another aspect of the present invention, the medication can be disposed in a single medicament container and can be loaded before each use. The loading receptacle may be specifically designed to hold the container for use whenever needed. In such a configuration, the receptacle is easily reached to facilitate rapid replacement of the medicament container is necessary.
In accordance with a preferred embodiment of the invention, the secondary inhalation passage feeds into a distal portion of the primary inhalation channel, i.e. distally from the rotatable vane, or into a common channel. Thus, the user places his or her mouth at the distal end of the primary inhalation channel and inhales. Initially, airflow is exclusively through the primary inhalation channel. However, as the rotatable vane rotates into a blocking or inhibiting position, it significantly interferes with airflow from the proximal end to the distal end of the primary inhalation channel. At the same time, movement of the rotatable vane moves the blocking member, thereby allowing airflow through the secondary inhalation passage-dispensing medicament into the distal portion of the primary inhalation channel or a common channel. During such, the user is obtaining a significant portion of the air inhaled through the secondary inhalation passage. This air carries the medicament to the patient""s lungs. The rotatable vane may either continue to rotate, ultimately rotating into a position wherein it no longer provides a significant impediment to flow through the primary inhalation channel, or the rotatable vane may be held in a position in which it restricts inspiratory air flow until inhalation is completed. When the rotatable vane continues to obstruct airflow through the primary inhalation passage, the user is forced to inhale more slowly and deposition of the medicament in the deep lung is maximized.
Once inhalation is completed, the rotatable vane returns to its original position. Likewise, the blocking member returns to its biased or closed position where it blocks airflow through the secondary inhalation passage.
Also in accordance with a presently preferred embodiment, the impact surfaces may either be disposed in the secondary inhalation passage, or in the distal portion of the primary inhalation passage or common passage at a location which is distal to the point at which the secondary inhalation passage feeds into the primary inhalation passage. Thus, the impact surfaces may be formed as nonlinear walls along the distal portion of the primary inhalation passage which are configured for contacting by the medicament particles after they have reached full velocity while entrained in the air flow. In such a position, the impact surfaces ensure that any large agglomerations are broken up prior to leaving the device.